For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningInstallation Procedure
Drill 8 mm (5/16 in) for plug welding along the edges of the service
panel as noted from the original
panel.
Clean and prepare the attaching surfaces for welding.
Position the body lock pillar inner panel on the vehicle.
Verify the fit of the panel.
Clamp th ...
Installation Procedure
Remove rear end upper panel extension (1) from service part.
Cut the body side inner panel in corresponding locations to fit the
remaining original panel. The sectioning joint should be trimmed to
allow a gap of one-and-one-half-times the metal thickness at the sectioning
jo ...
Transmission
Driver Shift Control (DSC) allows the automatic transmission to be shifted similar
to a manual transmission.
Electronic Range Select (ERS) allows for the selection of a range of gears.
Up-Shift Light
If the vehicle has a manual transmission, it will have an up-shift light that
indicates whe ...